A fuel cell is an energy conversion device that generates electricity and heat by electrochemically combining a gaseous fuel, such as hydrogen, carbon monoxide, or a hydrocarbon, and an oxidant, such as air or oxygen, across an ion-conducting electrolyte. The fuel cell converts chemical energy into electrical energy. A fuel cell generally consists of two electrodes positioned on opposites of an electrolyte. The oxidant passes over the oxygen electrode (cathode) while the fuel passes over the fuel electrode (anode), generating electricity, water, and heat. There are several types of fuel cells, including proton exchange membrane (PEM) fuel cells and solid oxide fuel cells (SOFC).
A SOFC is constructed entirely of solid-state materials, utilizing an ion conductive oxide ceramic as the electrolyte. A SOFC operates at high temperatures (e.g., temperatures of about xe2x88x9240xc2x0 C. up to about 1,200xc2x0 C.). A conventional electrochemical cell in a SOFC is comprised of an anode and a cathode with an electrolyte disposed therebetween. In a typical SOFC, a fuel flows to the anode where it is oxidized by oxygen ions from the electrolyte, producing electrons that are released to the external circuit, and mostly water and carbon dioxide are removed in the fuel flow stream. At the cathode, the oxidant accepts electrons from the external circuit to form oxygen ions. The oxygen ions migrate across the electrolyte to the anode. The flow of electrons through the external circuit provides for consumable or storable electrical power. However, each individual electrochemical cell generates a relatively small voltage. Higher voltages are attained by electrically connecting a plurality of electrochemical cells in series to form a stack.
The fuel cell stack also includes conduits or manifolds to allow passage of the fuel and oxidant into and byproducts, as well as excess fuel and oxidant, out of the stack. Generally, oxidant is fed to the structure from a manifold located on one side of the stack, while fuel is provided from a manifold located on an adjacent side of the stack. The fuel and oxidant are generally pumped through the manifolds and introduced to a flow field disposed adjacent to the appropriate electrode. The flow fields that direct the fuel and oxidant to the respective electrodes typically create oxidant and fuel flows across the electrodes that are perpendicular to one another.
The long term successful operation of a fuel cell depends primarily on maintaining structural and chemical stability of fuel cell components during steady state conditions, as well as transient operating conditions such as cold startups and emergency shut downs. The support systems are required to store and control the fuel, compress and control the oxidant and provide thermal energy management.
Generally, SOFC stacks are wrapped with an insulation to insulate the stack and retain the heat. Currently, the auxiliary power unit system expends fuel to provide thermal energy to the fuel cell stack. However, to maintain the thermal energy within the fuel cell stack, more and thicker insulation is required.
The drawbacks and disadvantages of the prior art are overcome by the thermophotovoltaic insulation for a SOFC system.
A fuel cell system is disclosed, which comprises a thermophotovoltaic insulation disposed in thermal communication with at least a portion of a fuel cell.
A method of operating a fuel cell system is also disclosed. The method comprises disposing a thermophotovoltaic insulation in thermal communication with a fuel cell. The fuel cell system is then operated to produce thermal energy. The thermal energy is then harnessed by the thermophotovoltaic insulation and transformed into electricity.
A fuel cell system is disclosed. The fuel cell system comprises a fuel cell stack comprising a plurality of fuel cells. A fuel supply and an oxidant supply are disposed in fluid communication with the fuel cell stack. A thermophotovoltaic insulation is disposed around at least a portion of the fuel cell stack. The thermophotovoltaic insulation comprises a selective emitter and a photovoltaic converter.
A fuel cell system is disclosed. The fuel cell system comprises a fuel cell and a means for producing electricity from thermal energy harnessed from the fuel cell.